Understanding acidogenesis towards green hydrogen and volatile fatty acid production-Critical analysis and circular economy perspective

Acidogenic fermentation of biomass/waste/wastewater for the generation of short-chain fatty acids (VFAs) is gaining interest associated with the production of bioenergy (biohydrogen (bio-H2) or methane (CH4)) due to their huge market potential. However, due to the optimization of production yields, knowledge of the intricate microbiological pathways, and selection of cost-effective VFAs separation techniques, scaling up and commercialization remain the challenges of the acidogenesis. The review thus illustrates the understanding of biotechnological interventions towards microbial distribution like the microbiota associated with hydrolytic, syntrophic and production activities. The abiotic and biotic factors impacting acidogenic productivity and the overview of important separation techniques are also discussed. For maximizing resource recovery, this review also offers insight into a variety of process integrations within the framework of a closed-loop biorefinery. The placement of acidogenesis in the present circular economy (CE) perspective was also discussed with reference to multi-product recovery. This review thus aims to offer a comprehensive perspective on the optimization, applications, separation of acidogenic products, sustainability analysis, and placement of the current acidogenic process in the current economy.